Free piston pumping system



July 2, 1963 N. F. BROWN ETAL Q 3,

FREE PISTON PUMPING SYSTEM Filed Dec. 2, 1959 5 Sheets-Sheet 1 A arman F. Brown CV/f/b/d M Pe ters ATTOR/Vf VJ July 2, 1963 N. F. BROWN ETAL 3,095,819

FREE PISTON PUMPING SYSTEM Filed Dec. 2, 1959 5 Sheets-Sheet 2 Norma/7 F. Brown (bf/ore M fie zel's July 2, 1963 N. F. BROWN ETAL 3,095,819

FREE PISTON PUMPING SYSTEM Filed Dec. 2, 1959 5 Sheets-Sheet 3 I we ATTORNEYJ July 2, 1963 N. F. BROWN ETAL. 3,

FREE PISTON PUMPING SYSTEM Filed Dec. 2, 1959 5 Sheets-Sheet 4 a; a; as 13 July 2, 1963 Filed Dec. 2, 1959 N. F. BROWN ETAL 3,0 5, 9

FREE PISTON PUMPING SYSTEM 5 Sheets-Sheet 5 zgg 82 Norma/7 F. Brown Chf/On/ M Pezers This invention is an improved free piston pumping system for raising oil or other liquid from wells by pressure of a gas. In one aspect it relates to an entire improved free piston pumping system. In another aspect it contemplates an improved control for such pumping actuated by presence of a free piston in a lubricator, and in another aspect it relates to an improved release for a free piston. In another aspect it relates to an improved pneumatic control system for a free piston pumping cycle.

Free piston pumping apparatus has been used in the petroleum industry for many years. In such installations a free piston is propelled by gas pressure through a string of production tubing from a production zone to a wellhead, pushing a load of liquid ahead of it. An upright section of pipe and associated fittings, commonly called a lubricator, having a bore in common with that of the production tube, extends above a wellhead and has one or more outlets for fluid communicating with it.

The free piston has an axial opening through it and a valve suitably arranged for opening and closing this opening. This valve usumly is operated by contact with a suitable bumper at the top of the lubricator and a bumper supported near the lower end of the production tubing, although pressure differential devices for operating such valves also are used. When this valve is open, permitting free passage of gas or liquid through the free piston, the piston falls in the well until it arrives at the production zone and the valve is closed, shutting off the passage through the piston.

Gas pressure, which may be pressure from gas introduced into the well for this purpose, or pressure from gas produced from the production formation or both, then forces the piston up the production tubing pushing its load of liquid ahead of it.

In low production wells it is customary to delay the time between reciprocating strokes of the piston to permit accumulation of fluid in the bottom of the well. Such delay between piston strokes in high producing Wells also may be necessary in order to meet requirements of regulations concerning production quotas.

A catcher is often provided in the lubricator section for the purpose of holding the piston at the top of the well for any desired length of time. Such catchers have been mechanically, pneumatically or solenoid operated and comprise a latch adapted to fit into suitable receiving spaces in the free piston. Catchers have been controlled by suitable timing devices, thus making operation automatic. Difficulties often are encountered in maintaining suitable pressure tight packing around moving parts of catchers. Complicated electrical controllers difficult to maintain under oil production conditions have been used for determining the length of time between strokes of the piston.

It is an object of this invention to provide an improved free piston pumping system in which the above difficulties are eliminated. Another object is to provide an improved free piston, lubricator and catcher assembly in which seals around moving parts are eliminated. Another object is to provide an improved simple, cheap, mechanical controller for the system eliminating difficulties in maintaining electrical systems. Still another object is to provide a modification applicable to wells producing both oil and gas in which oil and gas are automatically separated and passed to separate lines. An-

' 3.09am: Patented July 2, 1363 other object is to provide a modification particularly useful in pumping wells in which pressure or resistance to travel of a free piston are sufliciently variable to make the time of travel of a free piston from a production zone to a wellhead erratic. Another object is to provide a free piston pumping system in which a valve in an outlet is operated in response to the presence of the piston in a lubricator.

Other objects, advantages and features of this invention will be apparent to one skilled in the art upon consideration of the written specification, the attached claims and the annexed drawings.

In this invention a simple and dependable mechanical system is provided for releasing a catcher and operating a valve in an outlet line substantially simultaneously. In its preferred form a lubricator having a section made of non-magnetic material, preferably stainless steel, is superimposed on a wellhead. A production line extends down from the wellhead into a production zone and has a bore in common with that of the lubricator, thus permitting reciprocating travel of the free piston in the line from the production zone to the non-magnetic section of the lubricator. The free piston used contains magnetic material and preferably is made of steel. An outlet line for fluids pumped communicates with the bore of the lubricator. For wells producing both oil and gas this line preferably is branched, having one branch communicating with the lubricator above the point of maximum ravel of the free piston and the other branch communicating with the lubricator below the free piston at its upper limit of travel. An adjustable choke preferably is disposed in the outlet line or in its upper branch to prevent arrival of the piston at too high velocity.

Alternatively, the outlet line may lead from the wellhead, but in any case it leads from the common bore of the lubricator and production line.

A normally retracted movable magnet is disposed at the side of the non-magnetic section of the lubricator in position to be moved toward the lubricator by attraction to the free piston when the piston is in the lubricator. Movement of this magnet toward the lubricator opens a leed valve releasing pressure from a common line supplying pneumatic pressure both to a pressure responsive means for releasing spring pressure on the catcher and to one side of a diaphragm operating a valve opening and closing the outlet line. Substantially simultaneous operation of the valve and catcher in response to presence of the piston in the lubricator are thus obtained. Pressure in the common line joining the pressure operated valve and the pneumatic pressure actuated means opposing spring pressure on the catcher is restored by action of a pilot valve controlled by a timer, and communicating with a supply of gas under pressure. p

In a preferred modification the valve in the outlet line is a triple position valve. Suitable pneumatic relays, or shuttle valves, for switching gas pressure are provided, and function as means to maintain correlation between the positions assumed by this valve and the operation of the catcher, as will appear more clearly from the detailed description set out below.

In another modification, particularly useful in pumping wells whose pressure and resistance to travel of a free piston are sufiiciently variable as to make the time of travel of a free piston to the wellhead erratic, the magnetically opened bleed valve releases pressure from one side of a diaphragm in a valve motor closing the valve in the outlet line. A catcher may or may not be used, depending on the pumping cycle desired.

In the drawings, wherein like reference characters are used throughout to designate like parts:

FIG. 1 illustrates a free piston pumping system in which a pneumatic pressure responsive piston disposed to oppose and release spring pressure on the catcher and a pressure actuated motor valve in an outlet line from the lubricator are operated from a common line applying pneumatic pressure on the piston and the valve. The application and release of pressure is time controlled.

FIG. 2 shows an application of the magnetic pressure release of the invention applied to a free piston pumping system having a manually operated catcher.

FIG. 3 is a detail of a preferred magnetic release valve.

FIGS. 4, and 6 show different phases of cycle in one preferred free piston pumping system applicable to wells producing commercial quantities of gas and large quantities of liquid which may be either water or oil.

FIG. 4 shows the cooperation of parts during that part of the pumping cycle in which gas is produced from the well with the free'piston held stationary in the lubricator and gas is delivered to a gas outlet line.

. FIG. 5 shows the apparatus of FIG. 4 with the well in shut-in position with the catcher in retracted position and the piston dropped from the lubricator.

FIG. 6 shows the catcher with spring pressure released, the piston returning from the bottom of the well and the valve in the outlet line in position to deliver liquid to a liquid outlet line.

FIG. 1 shows a conventional wellhead designated by the numeral 10. The wellhead contains a gate valve 11. A line of production tubing 12 extends down from the Wellhead to a producing zone. In the producing zone a bumper 13 is disposed within the production line in position to contact the bottom of a free piston 19 at its lower limit of travel. Usually the production line is concentric with casing 14 as illustrated, leaving an annular space 15 between the production line and casing 14. When it is necessary to introduce gas under pressure to operate a free piston the gas is introduced by one or more lines 16 into the annular space 15 thus applying pressure beneath the free piston in the bore of the production tube 12.

An upright lubricator section comprising a pipe and suitable fittings designated generally as 17 is superimposed upon the wellhead. This lubricator has a bore 18 common to that of the production line. A free piston 19 is disposed within bore 18 for free travel therein from bumper 13 in the production zone to bumper 23 in an upper part of the lubricator.

Piston 19 has a suitable number of guide rings 21, spaced from each other and has a valve 22 adapted to be closed by contact with bumper 13.

A second bumper 23 is located in an upper part of the lubricatorand functions to open valve 22 by contact with a suitable valve rod 40.

A catcher, designated generally as 24 is disposed at the side of lubricator 17. In the preferred form illustrated, this catcher comprises a ball 25 actuated by pressure from a spring 26, disposed to move ball 25 far enough into the lubricator bore to engage a space between rings on piston 19 and so hold the piston stationary in the lubricator. Pneumatic pressure responsive means for re leasing spring pressure on ball 25 is illustrated as a piston 27, operated by pneumatic pressure applied through line 28.

An outlet 29, having two branches 31 and 32 leads from lubricator 17. The upper branch 31 communicates with the lubricator bore at a point above that reached by the piston at the upper end of its stroke. Branch 31 is equipped with an adjustable choke 33 to prevent arrival of the piston at too high velocity. I

A pneumatic pressure responsive valve 134 is disposed to open and close line 29 at a point downstream from the junction of branches 31 and 32. Line 28 communicates with a space above diaphragm 35 in the motor valve opening and closing line 29.

Pressure is applied and released upon diaphragm 35 and piston 27 simultaneously through line 28 by action 4 of a conventional timer controlled pilot valve designated generally as 34.

This valve contains a valve closure member 39 adapted to seat upon an inlet 36 from a supply line 37 and so shut oif entrance of gas supplied under pressure via line 37 from a source of supply (not shown). Member 36) is equipped with a pin 38 loosely fitting in an opening 39 communicating with the atmosphere. The upper end of member 30 is shaped to seat upon and close opening 39 in the upper part of the valve body.

A pivoted weight bar 41 is disposed to rest upon the upper end of pin 38. Bar 41 carries an adjustable saw tooth cam 42. A timer, preferably driven by mechanical clock work, having a face plate 43 carrying pins 44 disposed to strike cam 42 and raise weight bar 41 is provided.

Normally weight bar 41 rests upon pin 38 of valve 34 forcing valve closure member 33 to seat upon inlet 36 from a gas supply line and venting line 23 to the atmosphere by way of opening 39 around pin 38. Pneumatic pressure is thus relieved through line 28 from the upper side of diaphragm 35 and from piston 27. Spring 45 then holds the valve 134 open, allowing gas from the Well to flow through line 29 and branch 32. Spring pressure from spring 26 forces ball forward to engage free piston 19 on arrival and hold it stationary in the lubricator.

When the timer comes on time a pin 44 strikes the saw tooth cam 42 thus raising weigh-t bar 41. Pressure of supply gas then lifts valve member 30 from its seat on inlet 36, closes the opening 39 and permits the supply gas to flow around the member 33 into line 28, thus introducing pneumatic pressure into the spaces above diaphragm 3S and behind piston 27 in the catcher. Valve 134 then is closed interrupting the flow of gas from the well and the catcher is released. The Weight of piston 19 forces ball 25 back out of engagement with the piston 19 and the piston falls to the production zone in the well where it encounters bumper 13.

The time of contact of cam 42 with pin 44 is such that pressure is applied to diaphragm 35, closing valve 134, for a period sufficient for the free piston to fall into the production zone. In the production zone the free piston strikes bumper 13 closing valve 22 and the timer moves so that cam .2 falls behind pin 44 thus permitting weight bar 41 again to depress pin 38 closing the inlet for gas supplied under pressure in valve 34 and venting line 28 to the atmosphere. Valve 34 is thus opened and spring pressure applied to ball 25 in the catcher. The free piston rises forcing its load of liquid ahead of it. When the free piston arrives in the lubricator it is caught and held stationary by a ball 25 and the cycle of operations is repeated.

FIG. 2 illustrates a modification of the apparatus particularly useful in wells of such varying pressure as to make cycle control of the tree piston by a timer undesir able.

A lubricator designated generally as 51 is shown superimposed upon a wellhead having a gate valve 11 therein. A production line 12 extends down from the wellhead to a production zone and has a bore in common with that of lubricator 51. A free piston 19 is disposed to travel freely in the bore of production line 12 and lubricator 51. A manually operable catcher designated generally as 52 is attached to lubricator 51. Although a manually operated catcher is shown, its portrayal is not intended to exclude the use of a catcher of the type designated generally as 24 in FIG. 1 or other type catcher, since manually operated catchers are used only when the Well is to be shut downor when long delay between pumping cycles is desired. The lubricator has a section 53 of non-magnetic material, preferably of stainless steel. An outlet line 29 communicates with the bore of the lubricator through an upper line 54 having a manually operable choke 33 therein.

A movable magnet 55 is disposed at the side of the non-magnetic section of the lubricator 53 in position to be attracted to and move toward piston 19 when 1t 15 in the lubricator. Piston 1? is made of magnetic material, preferably of steel. Magnet 55 is carried on a pivoted bar 56. Movement of bar 56 toward the lubricator opens a bleed valve designated generally as 57 and shown 1n detail in FIG. 3 in a preferred form. A timer having a time wheel 43 carrying pins 44 is disposed to raise a weight bar 41 by contact with a saw tooth cam 42 as described under FIG. 1 above.

A pilot valve 34 identical to that described 1n FiG. l is operated by weight bar 41. A line 58 commun cates with the interior of the valve body 34 and contains a check valve 59 which prevents back flow of gas under pressure in the direction of valve 34. Line 58 communicates with the space above diaphragm in motor valve 61 which operates a valve closure member 62 by a suitable valve stem. The space above the diaphragm in motor valve 61 also communicates with line 63 leading to the bleed valve 57 operated by magnet 55.

This arrangement is particularly desirable for use with wells whose pressure characteristics vary so much that the time for return of the free piston cannot be accurately determined. Check valve 59, line 63 and bleed valve 57 cooperate to maintain pressure on the diaphragm in motor valve 61 to keep valve 62 open until the free piston returns to the lubricator. The presence of the free piston thus is necessary to permit valve 62 to close by releasing pressure through bleed valve 57 The system can be made completely automatic and self-regulatory by replacmg the manual catcher 52 with a catcher illustrated in FIG. 1 as is shown in the descriptions of FIGS. 4, 5 and 6 below.

In the preferred type of magnetic pressure release valve, shown in FIG. 3, a permanent magnet 65, preferably of horse shoe shape, is attached to a pivoted bar 66. Bar 66 turns on a shaft 67 and the magnet is normally retracted from the non-magnetic section of the lubricator by pressure of spring 63. Bar 66 carries a valve closure member 71 in position to seat upon and close a bleed orifice 72 connecting with line 63. In normal position pressure is sealed within line 63 and is released only when magnet 65 is attracted toward the free piston when the piston is in the lubricator. The forward movement of magnet 65 opens the bleed passage 72, as shown in the drawing, permitting pressure to be bled from above the diaphragm in motor valve 61.

FIGS. 4, 5 and 6 illustrate a modification of the system which is particularly advantageous for use with wells producing commerical quantities of gas and large quantities of liquid. In these figures a lubricator designated generally as 51 is shown. Lubricator 51 has a section 53 made of non-magnetic material, preferably stainless steel. A free piston 19 containing magnetic material and preferably made of steel is disposed to reciprocate 'fireely in the common bore 18 of lubricator 51 and a line of production tubing (not shown). A catcher designated generally as 24 of the type shown in FIG. 1 is disposed at a side of the non-magnetic section of the lubricator. This catcher comprises a ball 25 adapted to be pressed forward in response to pressure from spring 26 into the lubricator bore far enough to engage a space between rings 21 on piston 19 and thus hold the piston stationary in the lubricator. A pneumatic pressure responsive piston 27 is disposed :to oppose and release spring pressure actuating ball 25. A movable magnet 65 is disposed at a side of the non-magnetic section of the lubricator in position to be attracted by and moved toward piston 19 when the piston is in the lubricator. Magnet 65 is attached to a pivoted bar 66 carrying a valve closure member 71. A bleed valve designated generally as 73 is normally closed by valve closure member 71 in response to pressure from spring 68 when the piston is not in the lubricator.

An outlet line 29 has upper and lower branches 74 and 75, respectively, communicating with the bore of the lubricator. Branch 74 communicates with the lubricator at a point above the upper limit of travel of piston 19 and the lower branch 75 communicates with the interior of the lubricator at a point beneath the position occupied by the piston when held by the catcher. A three position pneumatically responsive motor valve designated generally as 76 is disposed to close line 29 or to pass fluid from line 29 to a line 168, or line 77, according to the position of the valve. Two pneumatic relays, or shuttle valves, designated generally as 78 and '79, are provided to correlate action of valve 76 and catcher 24.

FIG. 4 shows the system in position for production of gas. Free piston 19 is held in lubricator 51 by engagement with ball 25 which is forced into engagement by spring 26. Magnet 65 is attracted by piston 19 and has moved toward the lubricator, drawing with it pivoted bar 66, carrying valve closure member 71 thus opening release valve 73. Pressure has been vented to the atmosphere from line 81, communicating with the space behind piston 27 in catcher 24 and with line 32 leading to valve 73.

Line 82 also communicates with a space behind piston 83 in relay 78 via line 8d. Pneumatic pressure on piston 83 has thus been released, permitting pressure from spring 85 to shift piston 83. Relay 78 comprises a shaft 86 carrying sealing members 87 arranged for reciprocating movement in a cylinder $8 and attached to piston 83.

Movement of piston 83 admits gas under pressure from supply line via lines 89, dd and 91 to the upper side of diaphragm 92 in a valve motor designated generally as 93.

Line 91 also communicates via line $4 with a space in relay 79 and pressure is applied to piston 9'5 compressing spring 96, and moving shaft 97 carrying sealing members 87 into position to vent pressure from the underside of diaphragm 92 via line 8 and vent 99. Diaphragm 92. springs down to the full extent of its travel. Valve stem 101 is actuated by movement of diaphragm Valve stem 101 carries a flanged shoe 102. Two annular valve closure members 103 and 164 fit and slide upon shoe 16 2. A spring 105 is arranged to exert pressure on closure members 108' and 104 tending to force them apart.

At the position of maximum travel of valve stem 1191 downward, valve closure member 104 is seated on valve seat 166 thus closing oii line 77. Closure member 103 is forced downward by flange 107, compressing spring 105 and permitting flow from line 29 into line 168.

In this position the well is free to produce gas via bore 18, lower branch 75 of the outlet line 29, valve 76 and line 1113. The latter line conducts gas to sales, storage or use as desired.

This part of the production cycle continues for a period controlled by the timer. After a predetermined time selected by spacing of pins 44 on the time wheel 43, a pin 44 reaches cam 42 and lifts weight bar 41 as shown in FIG. 5. Gas under pressure enters from supply line 89 via line 1199 and pilot valve 34 into line 82. Lines 89, 109 and 82 have inside diameters larger than bleed valve 73. Pressure of gas entering through line 81 builds up in catcher 24 forcing piston 27 back and relieving spring pressure on ball 25. The free piston then drops out of lubricator 51, and bleed valve 73 closes in response to pressure from spring 68.

At the same time gas under pressure enters relay 78 from line 82 via line 84- and forces piston 83 back, cornpressing spring 85 and releasing pressure on the upper side of diaphragm 93 through line 11 and vent 1111. Pressure on piston 9'5 in relay 79 also is released through vent 111, but pressure from line 82 is simultaneously applied to piston 112 at the other end of relay 7? and the relay does not change position. That part of the valve motor 93 below diaphragm 92 continues to be vented to the atmosphere through line 93 and vent 59.

With no pressure above or below the diaphragm the valve motor assumes an intermediate position, moving 7 valve stem dill with it. In this intermediate position valve closure member 104 remains seated on seat 1% closing oif line 77. Valve closure member 1% is forced upward by spring 1&5 to close off line M8.

The Well is shut in so long as valve 76 remains in this position. A period of time long enough to permit the free piston to reach the bumper in the production zone is predetermined by the operating width of saw tooth cam 42. This cam preferably is adjustable, as shown in FIG. 1, to permit setting for any time required to permit the piston to reach the production zone.

After sufiicient time to permit the free piston to reach the bottom bumper the cam 42drops oft pin 44, as shown in FIG. 6. Weight bar 41 closes pilot valve 34 against gas entering from supply line 89 and relieves pressure on piston 1-12 in relay 79 through vent 39 in pilot valve 34 and the part of line 82 between check valve 59 and relay 79.

Relief of pressure on piston 112 permits spring 96 to operate the relay 79, connecting gas supply line 89 with line 98, thus applying pressure to the underside of diaphragm 92. Pressure in line 82 downstream of check valve 59 is maintained by check valve 59 and the seated position of valve closure member 71 on relief valve 73, maintaining relay 78 in position to vent pressure from the upper side of diaphragm 92 via line 91 and vent 111, and maintaining pressure on piston 27 compressing spring 26.

Diaphragm 92 is moved to its upper limit of travel by pressure on its lower side and carries valve stem 1M with it. Valve closure member 163 remains in position to close off line 168 and valve closure member 194 is drawn upward off seat 166 compressing spring 1135 and opening line 77 to flow of fluid from line 29.

A free piston =19 comes up bore 18 pushing a load of liquid ahead of it. The liquid flows through the lower branch 75 until this branch is obstructed by the piston; liquid then flows through the upper branch 74, line 29 and valve 76 into line 77, until the piston reaches its upper limit of travel.

When piston 19 arrives in a position opposite magnet 65 the magnet is attracted to the piston and moves the pivoted bar 66, carrying valve closure member 71, toward the lubricator, opening relief valve 73. Pneumatic pressure on piston '27 in the catcher is released via lines 81 and 82 and valve 73, pressure from spring 26 moves ball 25 forward, and the piston is caught and held.

Pressure in line 82 and on piston 83 in relay 78 is released through relief valve 73 and the cycle of operations described above under FIGS. 4, 5 and 6 is repeated.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with'other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed l. A free piston pumping system comprising in a combination a wellhead; a lubricator having a section made of non-magnetic material superimposed on the wellhead; a production line having a bore common to that of the lubricator extending down to a producing zone; a free piston containing magnetic material disposed to travel within the bore; a spring actuated catcher disposed to catch and retain the piston in the lubricator; pneumatic pressure responsive means for overcoming spring pressure on the catcher to move it to release the free piston; an outlet line leading from the bore; a pneumatic pressure responsive valve disposed to open and close the outlet line; a normally retracted movable magnet disposed at a side of the non-magnetic section of the lubricator in position to be moved by attraction toward the free piston when the piston is in the lubricator; and means, comprising a valve actuated by movement of the magnet, for bleeding pneumatic pressure from the pneumatic pressure responsive means for releasing the catcher to move to free piston catching position and from the pneumatic pressure responsive valve.

2. A free piston pumping system comprising in a combination a wellhead; a lubricator having a section made of non-magnetic material superimposed on the wellhead; a production line having a bore common to that of the lubricator extending down to a producing zone; a free piston containing magnetic material disposed to travel within the bore; a spring actuated catcher disposed to catch and retain the piston in the lubricator; pneumatic pressure responsive means for overcoming spring pressure on the catcher to move it to release the free piston; an outlet line leading from the bore; a pneumatic pressure responsive valve disposed to open and close the outlet line; and means, comprising a magnetically operable valve responsive to the presence of the free piston in the lubricator, for bleeding pneumatic pressure from the pneumatic pressure responsive means so as to release the catcher for movement to free piston catching position and from the pneumatic pressure responsive valve.

3. A free piston pumping system comprising in a combination a wellhead; a lubricator superimposed on the wellhead; a production line having a bore common to that of the lubricator extending down to a producing zone; a free piston disposed to travel within the bore; a catcher disposed to catch and retain the piston in the lubricator and biased to a piston catching position; pneumatic pressure responsive means for overcoming the bias on the catcher to move it to piston releasing position; an outlet line leading from the bore; a pneumatic pressure responsive valve disposed to open and close the outlet line; means, comprising a valve operable responsive to the presence of the free piston in the lubricator, for bleeding pneumatic pressure from the pneumatic pressure reponsive means to permit the catcher to move to piston catching position and from the pneumatic pressure responsive valve; and means, comprising a timer controller pilot valve, for applying pneumatic pressure to the pneumatic pressure responsive means to overcome the bias on the catcher and to the pressure responsive valve.

4. A free piston pumping system comprising in combination a wellhead; a lubricator having a section made of non-magnetic material superimposed on the wellhead; a production line having a bore common to that of the lubricator extending down to a production zone; a free piston containing magnetic material disposed to travel within the bore; a spring actuated catcher disposed to catch and retain the free piston in the lubricator; pneumatic pressure responsive means for releasing spring pressure from the catcher; a normally retracted movable magnet disposed at a side of the non-magnetic section of the lubricator in position to be moved toward the lubricator by attraction to the free piston when the piston is in the lubricator; a valve actuated by movement of the magnet; an outlet line leading from the lubricator bore; a three position pressure responsive motor valve, having one inlet and two outlets, having its inlet connected to a downstream end of said outlet line; a timer controlled two-way pilot valve having an inlet, an outlet and a vent to the atmosphere; two pneumatic relays, namely, a first relay and a second relay, each having a passage therethrough-and a vent adapted to be opened and closed by shifting of the relay, said first relay, having one pressure responsive means for shifting the relay and said second having two opposed pressure responsive means for shifting the relay; a supply line for gas under pressure connected with a passage in each of said relaysand with the inlet of said two-way pilot valve; a line communicating With the supply line for gas under pressure through a passage in said first relay, when the passage is open, with a first side of the pressure responsive motor valve and with the first of the two opposed pressure responsive means for moving the second relay and with a vent in said first relay when said first relay is shifted; a line connecting to the outlet of said two-way pilot valve and communicating with the second of the two opposed pressure responsive means for moving the second relay, with the pneumatic pressure responsive means for moving said first relay, with said pneumatic pressure responsive means for releasing spring pressure from the catcher and with said valve actuated by movement of the magnet; a check valve disposed in said last mentioned line to release pressure only on the second of the pneumatic pressure means for moving the second relay when the two-way pilot valve is vented to the atmosphere; and a line connecting the second side of the three position pressure responsive motor valve with said second relay communicating with said supply line for gas under pressure When the passage through the said second relay is open, and vented to the atmosphere by movement of the second relay.

5. A controller for a free piston pumping system comprising in combination a timer; a two-way pilot valve having an inlet, an outlet, and a vent to the atmosphere controlled by the timer; two pneumatic relays, namely a first relay and a second relay, each having a passage therethrough and a vent to the atmosphere adapted to be opened and closed by shifting the relay, said first relay having one pressure responsive means 'for shifting the relay and the second relay having two pressure responsive means for shifting said second relay; a supply line for gas under pressure connected with a passage in each of said relays and with the inlet of said two-Way pilot valve; a first line adapted to be connected to a first side of a pressure responsive motor valve and being connected with the first of the two pressure responsive means for moving the second relay, said first line also communicating with the supply line for gas under pressure through a passage in said first relay when the passage is open, and vented to the atmosphere when said first relay is shifted; a second line connected to the outlet of said two-way pilot valve communicating with the second of the two opposed pressure responsive means for moving the second relay, with pneumatic pressure responsive means for moving said first relay and with a magnetically operable relief valve, responsive to presence of a free piston, adapted to release pressure from the line; a check valve disposed in said last mentioned line to release pressure only on the second of the two pneumatic pressure means for shifting the second relay when the two-way pilot valve is vented to the atmosphere; and a third line adapted to connect a second side of a pressure actuated valve motor With the second relay and communicating with said supply line for gas under pressure when the passage through said second relay is open, and vented to the atmosphere when the second relay is shifted.

6. A free piston pumping system comprising in combination a wellhead; a lubricator having a section made of non-magnetic material superimposed on the Wellhead; a production line having a bore common to that of the lubricator extending down from the Wellhead to a production zone; a free piston disposed for reciprocating travel within the bore; a catcher disposed to catch and retain the free piston in the lubricator; pneumatic pressure-responsive means for releasing the catcher to permit the free piston to fall from the lubricator; an outlet line communicating with the bore; a pneumatic pressureresponsive valve disposed to open and close the outlet line; a common pneumatic pressure line connecting the means for releasing the catcher with the pressure-responsive valve; means for bleeding pressure from the common line including a magnet arranged for movement toward the lubricator in response to attraction of the free piston when the free piston is in said lubricator section; and a valve actuated by movement of the magnet.

7. A well pumping system comprising in combination a Wellhead; a lubricator having a section made of nonmagnetic material superimposed on the wellhead; a production line having a bore common to that of the lubricator extending down from the wellhead to a producing zone; a free piston containing magnetic material disposed for reciprocating travel within the bore; a catcher disposed to catch and retain the piston in the lubricator; pneumatic pressure-responsive means for moving the catcher to free piston-releasing position; means for operating said pneumatic pressure-responsive means to move the catcher to free-piston-releasing position including a magnet disposed adjacent to said non-magnetic section of the lubricator movable toward the lubricator in response to presence of the free piston in said non-magnetic section; and a valve operable by movement of said magnet.

8. A free piston pumping system comprising in combination a 'wellhead; a lubricator having a section made of non-magnetic material superimposed upon the wellhead;

a production line having a bore common to that of the lubricator extending down to a production zone; a free piston containing magnetic material disposed for reciprocating travel within the bore in a pumping cycle comprising three periods, namely, a period of travel down to the production Zone, a period of travel upward to the lubricator and a stationary period within the lubricator; an outlet line leading from the lubricator; a three-position pressure-responsive valve having an inlet port connected to said outlet line and first and second outlet ports; first and second product lines connected to said first and second outlet ports, respectively; and means comprising a timercontrolled pilot valve, a magnetically operable valve responsive to the presence of the free piston in the lubricator and pneumatic relay-s for causing the pressure-responsive valve to close the outlet line during the period of piston travel down to the production zone, to open the outlet line to the first product line during upward travel of the piston and to open the outlet line to the second product line upon arrival of the piston in the lubricator.

9. A free piston pumping system comprising in combination a Wellhead; a lubricator having a section made of non-magnetic material superimposed on the wellhead; a production line having a bore common to that of the lubricator extending down to a production zone; a free piston containing magnetic material disposed to travel within the bore in a pumping cycle comprising three periods, namely, a period of travel down to the production zone, a period of travel upward to the lubricator and a stationary period Within the lubricator; an outlet line leading from the lubricator; first and second product lines; a three-position pressure-responsive valve having an inlet connected to said outlet line and first and second outlet ports connected respectively to said first and second product lines, said valve having a position closing the outlet line, a position directing fiow from the outlet line into the first product line and a position directing flow from the outlet line into the second product line; and means comprising a timer-controlled pilot valve, a magnetically operable valve responsive to presence of the free piston in the lubricator and pneumatic relays cooperable with the pilot valve and magnetically operable valve to operate the three-position valve to cause said three-position valve to close the outlet line during down travel of the piston, to open the outlet line to the first product line during upward travel of the piston and to open the outlet line to the second product line during said stationary period.

10. A free piston pumping system comprising in combination a wellhead; a lubricator having a section made of non-magnetic material superimposed on the Wellhead; a

production line having a bore common to that of the lubricator extending down to a production zone; a free piston containing magnetic material disposed for reciproeating travel within the bore in a pumping cycle comprising three periods, namely, a period of travel down to the production zone, a period of travel upward to the lubri cator and a stationary period within the lubricator; an outlet line leading from the lubricator; a three-position pressure-responsive valve having an inlet connected to the outlet line and first and second outlet ports; a liquid product line connected to the first outlet port and a gas product line connected to the second outlet port; and means comprising a timer-controlled pilot valve, a magnetically operable valve responsive to the presence of the free piston in the'lubricator and pneumatic relays cooperable with the pilot valve and magnetically operable valve for positioning said three-position valve to maintain closure of the outlet line during travel of the free piston down to the production zone, to pass liquid from the outlet line into the liquid product line during upward travel of the free piston and to pass gas to the gas product line while the piston is stationary in the lubrioator.

11. A controller for a free piston pumping system comprising in combination a timer; a two-way pilot valve having an inlet, an outlet, and a vent to the atmosphere controlled by the timer; two pneumatic relays, namely, a first relay and a second relay, each having a passage therethrough and a vent to the atmosphere adapted to be opened and closed by shifting the relay, said first relay having one pressureresponsive means for shiftin g the relay and the second relay having two pressure-responsive means for shifting said second relay; a supply line for gas under pressure connected with the passage in each of said relays and with the inlet of said two-way pilot valve; a first line adapted to be connected to a first side of a pressureresponsive motor valve and connected with the first of the two pressure-responsive means for moving the second relay and said first line also communicating with the supply line for gas under pressure through a passage in said first relay when the passage is open, and vented to the atmosphere when said relay is shiited; a relief valve adapted to release pressure from the line; a second line connected to the outlet of said two-way pilot valve communicating with the second of the two pressure-responsive means for moving the second relay, with pneumatic pressure-responsive means for moving said first relay; a relief valve adapted to release pressure from the line connected into the second line; a check valve disposed in said second line to release pressure only on the second of the two pneumatic pressure-responsive means for shifting the second relay when the two-way pilot valve is vented to the atmosphere; and a third line adapted to be connected to a second side of a pressure-actuated valve motor and connected with a second relay and communicating with said supply line for gas under pressure when the passage through said second relay is open and vented to the atmosphere when the second relay is shifted.

12. A free piston pumping system comprising a production line extending in a well down to a production zone; a free piston adapted to travel up and down in the production line; an outlet line communicating with the production line; valve means controlling flow from the outlet line and having first and second outlet ports; trigger means adjacent the upper end of the production line and adapted to send a signal responsive to arrival of the free piston at the upper end of the production line; and control means, operable to cause the valve means to close the outlet line while the free piston is moving down in the production line, to open the outlet line to the first outlet port during upward travel of the free piston and then, responsive to said signal to open the outlet line to the second outlet port upon arrival of the free piston at the upper end of the production line, said control means including a timer and a free piston catcher positioned to catch and retain the free piston at the upper end of the production line, said control means being connected to the catcher so as .to cause the catcher to release the free piston upon lapse of a predetermined time interval and to cause the valve means to close the outlet line upon such release of the free piston.

References Cited in the file of this patent UNITED STATES PATENTS 2,001,552 Scott May 14, 1935 2,013,111 Scott Sept. 3, 1935 2,231,158 Davis Feb. 11, 1941 2,310,562 Whittington Feb. 9, 1943 2,575,086 Atchison Nov. 13, 1951 2,699,121 Knox Jan. 11, 1955 2,714,855 Brown Aug. 9, 1955 2,762,309 Knox Sept. 11, 1956 2,918,015 Knox Dec. 22, 1959 3,012,513 Knox Dec. 12, 1961 

1. A FREE PISTON PUMPING SYSTEM COMPRISING IN A COMBINATION A WELLHEAD; A LUBRICATOR HAVING A SECTION MADE OF NON-MAGNETIC MATERIAL SUPERIMPOSED ON THE WELLHEAD; A PRODUCTION LINE HAVING A BORE COMMON TO THAT OF THE LUBRICATOR EXTENDING DOWN TO A PRODUCING ZONE; A FREE PISTON CONTAINING MAGNETIC MATERIAL DISPOSED TO TRAVEL WITHIN THE BORE; A SPRING ACTUATED CATCHER DISPOSED TO CATCH AND RETAIN THE PISTON IN THE LUBRICATOR; PNEUMATIC PRESSURE RESPONSIVE MEANS FOR OVERCOMING SPRING PRESSURE ON THE CATCHER TO MOVE IT TO RELEASE THE FREE PISTON; AN OUTLET LINE LEADING FROM THE BORE; A PNEUMATIC PRESSURE RESPONSIVE VALVE DISPOSED TO OPEN AND CLOSE THE OUTLET LINE; A NORMALLY RETRACTED MOVABLE MAGNET DISPOSED AT A SIDE OF THE NON-MAGNETIC SECTION OF THE LUBRICATOR IN A POSITON TO BE MOVED BY ATTRACTION TOWARD THE FREE PISTON WHEN THE PISTON IS IN THE LUBRICATOR; AND MEANS, COMPRISING A VALVE ACTUATED BY MOVEMENT OF THE MAGNET, FOR BLEEDING PNEUMATIC PRESSURE FROM THE PNEUMATIC PRESSURE RESPONSIVE MEANS FOR RELEASING THE CATCHER TO MOVE TO FREE PISTON CATCHING POSITION AND FROM THE PNEUMATIC PRESSURE RESPONSIVE VALVE. 